Various blood processing systems now make it possible to collect particular blood constituents, instead of whole blood, from a blood source. Typically, in such systems, whole blood is drawn from a blood source, the particular blood component or constituent is separated, removed, and collected, and the remaining blood constituents are returned to the blood source. Removing only particular constituents is advantageous when the blood source is a human donor, because potentially less time is needed for the donor's body to return to pre-donation levels, and donations can be made at more frequent intervals than when whole blood is collected. This increases the overall supply of blood constituents, such as plasma and platelets, made available for transfer and/or therapeutic treatment.
Whole blood is typically separated into its constituents (e.g., red cells, platelets, and plasma) through centrifugation, such as in the AMICUS® separator from Fenwal, Inc. of Lake Zurich, Ill., which is an affiliate of Fresenius Kabi AG of Bad Homburg, Germany, or other centrifugal separation devices, or a spinning membrane-type separator, such as the AUTOPHERESIS-C® device from Fenwal, Inc.
In some of these systems, an optical device is provided for detecting the presence of hemoglobin in separated blood plasma. However, experience has shown that the presence of excessive lipids in the plasma may result in false hemoglobin alarms, due to the nature in which the optical device detects the presence of hemoglobin and difficulty that results in distinguishing hemoglobin from lipids. The presence of excessive lipids in plasma can also create difficulties in systems which attempt to quantify platelets being removed in plasma from a blood separator or which attempt to monitor the location of the interface between separated red cells and plasma during centrifugal separation. Accordingly, the need remains for a blood processing system which can better detect the presence of lipids in separated plasma.